But is the ISO bootable? if Yes it's simple you can do a clean install altough there is FAQ on Microsoft support site for windows 8 that says:

You upgraded to Windows 8, but didn't have a previous version of Windowsinstalled (error 0xC004F061)

If you see error 0xC004F061 when you try to activate Windows 8, it means that you're using a product key for an upgrade version of Windows 8 and a previous version of Windows wasn't on your PC when Windows 8 was installed. To install an upgrade version of Windows 8, you must already have Windows 7, Windows Vista, or Windows XP installed on your PC.If you formatted the drive before the upgrade version of Windows 8 was installed, you won't be able to use your upgrade product key to activate Windows 8. To activate Windows 8, you'll need to install your previous version of Windows, and then reinstall Windows 8. For help with the activation process, contact support.

But is the ISO bootable? if Yes it's simple you can do a clean install altough there is FAQ on Microsoft support site for windows 8 that says:

You upgraded to Windows 8, but didn't have a previous version of Windowsinstalled (error 0xC004F061)

If you see error 0xC004F061 when you try to activate Windows 8, it means that you're using a product key for an upgrade version of Windows 8 and a previous version of Windows wasn't on your PC when Windows 8 was installed. To install an upgrade version of Windows 8, you must already have Windows 7, Windows Vista, or Windows XP installed on your PC.If you formatted the drive before the upgrade version of Windows 8 was installed, you won't be able to use your upgrade product key to activate Windows 8. To activate Windows 8, you'll need to install your previous version of Windows, and then reinstall Windows 8. For help with the activation process, contact support.

Did you get that error with the 14.99 upgrade or the 24.99 upgrade? I hear the 14.99 upgrade has more limitations than the normally priced upgrade